The invention relates to a positive-locking connection between a metallic bridge and a moulded article which is injection-moulded from plastic, in particular for spectacles, with one end of the bridge engaging in the moulded article.
In order to connect the metallic cheek piece carrying the side joint with the plastic frame forming the frame for the glasses in such a way that this connection can be sufficiently loaded, the metallic cheek piece is inserted with its engaging end into the injection mould for the spectacle frame, so that the plastic of the frame is injection-moulded around the engaging end of the cheek piece. Due to the unavoidable tolerances, it may occur that there are difficulties in sealing the leadthrough of the metallic cheek piece through the injection mould, so that in the visible zone of the transition from the plastic frame to the metallic cheek piece it is necessary to rework the cheek piece. Moreover, it may occur that the surface of the frequently refined metallic parts is damaged by the insertion into the injection mould. An additional factor is that the insertion of the metallic parts into the injection mould can hardly be automated.
The invention is thus based on the object of providing a positive-locking connection between a metallic bridge and a moulded article of the kind mentioned above which is injection-moulded from plastic, in particular for spectacles, so that a connection with sufficient loading capacity can be produced with little effort without having to re-work the metallic bridge. Moreover, the danger of any damage to the surface of the metallic bridge is to be avoided.
This object is achieved by the invention in such a way that the moulded article forms a plug-in receiving means for the engaging end of the bridge which is provided with a wave-shaped snap-in profiling which, with a substantially elastic deformation of a wall profiling of the plug-in receiving means arranged according to the snap-in profiling of the bridge end, can be inserted into the same.
As a result of the plug-in connection between the moulded article made of injection-moulded plastic and the metallic bridge, all other disadvantages in connection with the insertion of said bridge into an injection mould are avoided. Conventional plug-in connections are unsuitable for such use due to the relatively high load requirements which are placed on spectacle frames. These load requirements can only be fulfilled by a wall profiling of the plug-in receiving means according to the snap-in profiling of the engaging end of the bridge when during the insertion of the engaging end of the bridge into the plug-in receiving means its wall profiling is deformed substantially only elastically by the projecting wave crests of the snap-in profiling of the bridge end, so that after the introduction of the bridge end into the plug-in receiving means the wave crests of the bridge end will engage in the wave troughs of the wall profiling of the plug-in receiving means without causing any local stresses which could lead to the formation of fissures in the zone of the wall profiling of the plug-in receiving means. The positive-locking connection produced in this manner between the metallic bridge and the moulded article which is injection-moulded from plastic is surprisingly capable of permanently withstanding all loads which occur in spectacles in particular. Concerning the connection load, conditions can certainly be obtained which are comparable with bridges which are injected into plastic. With the omission of injection-moulding around the bridge it is also possible to simplify storing because connections only need to be produced when needed and not during the production of the moulded bodies.
By influencing the shape of the wave-shaped snap-in profiling of the bridge end or the wall profiling of the plug-in receiving means, it is possible to take into account different load requirements. As a result, advantageous pre-conditions for a connection in accordance with the invention will be obtained when the snap-in profiling of the engaging end of the bridge consists of an undulation of mutually oppositely disposed bridge surfaces. Said undulation of the bridge surfaces can extend symmetrically with respect to the central plane of the bridge, so that thick places of the bridge are formed in the zone of the wave crests and thin places of the bridge are formed in the wave troughs. The symmetrical arrangement of the snap-in profiling to mutually oppositely disposed bridge surfaces makes the connection independent of any rotational position of the metallic bridge because corresponding profile outline shapes are obtained for the engaging end which is rotated by 180xc2x0 about its longitudinal axis. If, on the other hand, in another embodiment, the engaging end of the bridge is bent back and forth in a wave-like manner to form the snap-in profiling, these symmetrical conditions are left, which leads to a distinction between left and right spectacle parts.
The positive-locking connection between a metallic bridge and a moulded article which is injection-moulded from plastic allows new spectacle designs because the plug-in connection can also be made as late as during the assembly. It becomes possible for example to advantageously produce spectacle joints which consist of a cylindrical joint body which is rotatably held in the bearing bush of the cheek piece and which is connected with the wire side shaft. Since the wire side shaft of the spectacle is guided through a circumferential slot of the bearing bush and the cylindrical joint body can only be inserted axially into the bearing bush, it was necessary that the circumferential slot was provided with an axial leadthrough opening for the wire side shaft in order to enable the insertion of the wire side shaft connected with the joint body into the side joint. If the bearing body which is produced as a moulded part made of injection-moulded plastic forms a plug-in receiving means in accordance with the invention for the engaging end of the wire side shaft and if the engaging end of the wire side shaft is provided with a respective snap-in profiling, the engaging end of the wire side shaft, following the axial insertion of the joint body into the bearing bush, can be inserted from the outside through the circumferential slot of the bearing bush in the radial direction into the plug-in receiving means in order to ensure the required positive-locking connection. In this way, an axial retention of the joint body in the bearing bush is achieved which is effective over the entire swivelling range of the joint, namely with the help of the wire side shaft which is held in the circumferential slot of the bearing bush against a single displacement.
As has already been explained above, it is of relevant importance for the permanent resilience of the positive-locking connection that the wave-like snap-in profiling of the bridge end corresponds to the wall profiling of the plug-in receiving means, so that in the case of engagement no locally limited tensions will occur in the moulded article which could lead to an overload of the plastic although the connection stress remains within a permissible range. In order to enable the simple production of a respective plug-in receiving means for the engaging end of the metallic bridge which is provided with a wave-like snap-in profiling, an injection mould with a core for the plug-in receiving means can be provided for the moulded article which has the shape of the engaging end of the bridge. Since a moulded article with such a plug-in receiving means cannot be removed from the mould with ease and the elastic behaviour of the moulded article still must allow the insertion of the engaging end of the metallic bridge into the plug-in receiving means, the core, following the curing of the moulded article, can be pulled out by using the elastic behaviour of the wall profiling of the plug-in receiving means from the moulded article under elastic deformation of the wall profiling, so that advantageous constructional conditions for the injection moulds and simple mould removal conditions are obtained for the respective moulded articles which are produced with such injection moulds.